A cryptographic communication network is known that is configured with a plurality of networked nodes which is mutually connected by a plurality of links. Each node has the function of generating and sharing a random number with opposite nodes that are connected by links, as well as has the function of performing cryptographic communication over a link by using a random number as a cryptographic key (hereinafter, referred to as “a link key”). Moreover, some of the nodes also have the function of generating a random number independent of the links, as well as have the function of transmitting the generated random number to a different node. In a cryptographic communication network, an application has the function of obtaining a random number from a node, using that random number as a cryptographic key (hereinafter, referred to as “an application key”), and performing cryptographic communication with another application. Herein, an application can be configured in an integrated manner with the nodes, or can be configured as a terminal independent of the nodes.
In a node, the function by which a random number (a link key) is generated and shared with opposite nodes connected by links can be implemented using a technology that is commonly called quantum cryptographic communication. In this case, the technology by which, in a node, a random number (an application key) is generated independent of the links and transmitted to a different node via a link is called quantum key distribution (QKD).
However, in the conventional technology, an application that implements the cryptographic communication function using a cryptographic communication network needs to follow a complex sequence of operations such as in-advance address registration with respect to the cryptographic communication network, issuing of communication instructions to the cryptographic communication network, and obtaining of keys. For that reason, performing cryptographic communication from an existing application through the use of a cryptographic communication network is a difficult task.